[PATCH] D57632: [WebAssembly] Fix imported function symbol names that differ from their import names in the .o format

[Dan Gohman via Phabricator via llvm-commits]

sunfish created this revision.
sunfish added a reviewer: sbc100.
Herald added subscribers: rupprecht, dexonsmith, steven_wu, jgravelle-google, mehdi_amini.
Herald added a project: LLVM.

It appears that in the current .o file format, symbol names for undefined function symbols are not included, which means that we can't have symbols where the symbol name differs from the import name.

The following patch fixes it. (It includes both llvm and lld changes, as they're closely related, but I'll split them when committing.) With this patch, the following testcase:

  __attribute__((import_module("bar"), import_name("qux"))) void foo(void);
  
  void _start(void) {
      foo();
  }

compiles with `clang -nostdlib test.c --target=wasm32-unknown-unknown -Wl,--allow-undefined-file=undefined.txt

where undefined.txt contains:

  foo

into a wasm that contains this import:

  (import "bar" "qux" (func $foo (type 0)))

Since this requires a change to the binary form, this patch also bumps the metadata version number.


Repository:
  rL LLVM

https://reviews.llvm.org/D57632

Files:
  include/llvm/BinaryFormat/Wasm.h
  lib/MC/WasmObjectWriter.cpp
  lib/Object/WasmObjectFile.cpp
  test/MC/WebAssembly/assembler-binary.ll
  test/MC/WebAssembly/comdat.ll
  test/MC/WebAssembly/event-section.ll
  test/MC/WebAssembly/function-sections.ll
  test/MC/WebAssembly/global-ctor-dtor.ll
  test/MC/WebAssembly/unnamed-data.ll
  test/MC/WebAssembly/weak-alias.ll
  test/Object/Inputs/trivial-object-test.wasm
  test/Object/wasm-bad-metadata-version.yaml
  test/ObjectYAML/wasm/code_section.yaml
  test/ObjectYAML/wasm/data_section.yaml
  test/ObjectYAML/wasm/event_section.yaml
  test/ObjectYAML/wasm/invalid_global_weak.yaml
  test/ObjectYAML/wasm/linking_section.yaml
  test/ObjectYAML/wasm/weak_symbols.yaml
  test/tools/llvm-nm/wasm/exports.yaml
  test/tools/llvm-nm/wasm/imports.yaml
  test/tools/llvm-nm/wasm/weak-symbols.yaml
  test/tools/llvm-objdump/Inputs/trivial.obj.wasm
  test/tools/llvm-readobj/Inputs/trivial.obj.wasm
  tools/lld/wasm/InputFiles.cpp
  tools/lld/wasm/LTO.cpp
  tools/lld/wasm/SymbolTable.cpp
  tools/lld/wasm/SymbolTable.h
  tools/lld/wasm/Symbols.h
  tools/lld/wasm/Writer.cpp
  tools/yaml2obj/yaml2wasm.cpp

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